The present invention relates to a photochromic synthetic resin (i.e., plastic) object, characterized by a permanently increased contrast relative to that of photochromic synthetic resin objects available in the prior art. That is, the photochromic synthetic resin object according to the invention displays an improved contrast in the stationary state and in every phase, both during darkening as well as during bleaching or lightening. The inventive synthetic resin object can be used as a photochromic lens for eyeglasses, particularly for sports glasses.
Photochromic synthetic resin objects, in particular eyeglass lenses, have been commercially available since the 1980's. The first lens to find widespread distribution, for example Rodenstock Perfalit ColorMatic (since 1986) or the colored lens from Transitions Optical, Inc. (since 1990) marketed by several lens manufacturers as the Transitions lens, contained spirooxazines as photochromic dyes which darkened in a blue tint. Later products, such as the Transitions Plus gray lens (since 1992), the Transitions Eurobraun and Hoya Sunbrown brown lenses (since 1994), and the new Rodenstock Perfalit ColorMatic lens (since 1995) contained pyrans in addition to spirooxazines and/or fulgides. Products currently on the market, such as the Transitions III lens, preferentially use pyrans, especially naphthopyrans, and larger ring systems derived therefrom. The Transitions III products having a refractive index of 1.56 are based on U.S. Pat. No. 5,753,146.
The lenses currently available according to the prior art all have the common feature that said lenses do not exhibit satisfactory contrast as a result of illumination-dependent darkening.